Does any body know what a crank shaft sensor is?

Or a crank shaft fuel distrubutor is?

It's just that! It senses crankshaft revs. It's just a magnet that picks up pulses from a reluctor wheel on your crank end. Like unununununununuunun---ununununununun

It turns that into ac voltages and sends that to your cars computer then the computer counts them.
Notice the space in the diag. That count is figured in with the camshaft sensor. Everything must be in time or things will stop.
Kind of like this planet I'm on. Lol

Do you know where you can buy one?

Dealer only. What we working on? Maybe that's not the problem.

It's a sensor for a car, volkswagen polo

A crank sensor is a component used in an internal combustion engine to monitor the position or rotational speed of the crankshaft. This information is used by engine management systems to control ignition system timing and other engine parameters. Before electronic crank sensors were available, the distributor would have to be manually adjusted to a timing mark on the engine.
The crank sensor can be used in combination with a similar camshaft position sensor to monitor the relationship between the pistons and valves in the engine, which is particularly important in engines with variable valve timing. It is also commonly the primary source for the measurement of engine speed in revolutions per minute.
Crank sensors in engines usually consist of magnets and an inductive coil, or they may be based on magnetically triggered Hall effect semiconductor devices. Common mounting locations include the main crank pulley, the flywheel, and occasionally on the crankshaft itself. This sensor is the most important sensor in modern day engines. When it fails, there is a small chance the engine will start (engine will likely cut out after a few minutes of driving) but it mostly will not start.

The post above me is a great one and you can buy a crank sensor most likely from any near auto parts store like NAPA. They may have to order one to fit your car. Dealers sometimes charge too much for them and any other store doesn't have top of the line. You don't want it to fail again so I recommend going to NAPA